This application is based upon and claims the benefit of priority of Japanese Patent Application No. 2002-88300 filed on Mar. 27, 2002, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a valve timing adjusting apparatus that adjusts valve opening and closing timing (a valve timing) of at least one of an intake valve and an exhaust valve of an internal combustion engine (engine) and a method of controlling the same.
2. Description of Related Art
There is known a valve timing adjusting apparatus in which valve timing of at least one of an intake valve and an exhaust valve is adjusted by hydraulically controlling angular phase of a driven side rotating member rotatable together with a camshaft relative to a drive side rotating member receiving drive force from a crankshaft of an engine and rotatable together with the crankshaft, that is, controlling angular phase of the camshaft relative to the crankshaft to a given value.
According to a conventional vane type valve timing adjusting apparatus, a vane as the driven side rotating member is accommodated in the drive side rotating member in such a manner that angular phase of the vane relative to the drive side rotating member is variable and defined by controlling hydraulic pressure applied to the vane. Further, according to another conventional valve timing adjusting apparatus, a drive force transmitting member disposed between the drive side rotating member and the driven side rotating member is provided with a helical spline engagement mechanism and angular phase of the driven side rotating member relative to the drive side rotating member is varied by hydraulically moving reciprocatingly the drive force transmitting member.
In the valve timing adjusting apparatus mentioned above, it is preferable for a purpose of preventing engine cranking failure when the engine is cranked that the valve timing of at least one of the intake valve and the exhaust valve is kept at a middle between the most retard timing and the most advanced timing that is the most adequate timing for securing efficient engine cranking.
For example, in the valve timing adjusting apparatus in which a piston is provided in the driven side rotating member and a fitting hole, in which the piston can be fitted, is provided in the drive side rotating member, the angular phase of the driven side rotating member relative to the drive side rotating member is locked to the middle position between the most retard angular position and the most advanced angular position by inserting the piston into the fitting hole when the engine stops. Operation of fitting the piston in the fitting hole or operation of pulling the piston out of the fitting hole is controlled by force balance between biasing force of a spring urging the piston toward the fitting hole and hydraulic pressure acting on the piston in a direction in which the piston is pulled out of the fitting hole.
Further, in a certain engine condition, for example, in a case of rapidly reducing vehicle speed during a period when the vehicle is running at high and constant speed, it is preferable for preventing abnormal engine operation that the valve timing is held within a limited range between the most retard timing and the most advanced timing by controlling the angular phase of the driven side rotating member relative to the driven side rotating member to keep within an angular range corresponding to the limited range.
For example, in the valve timing adjusting apparatus in which the drive side rotating member is provided with an arc shaped restriction hole extending in a direction in which the driven side rotating member rotates relatively to the drive side rotating member and the driven side rotating member is provided with a piston that can be inserted into the restriction hole, the angular phase of the driven side rotating member relative to the drive side rotating member is controlled within an angular range defined with opposite ends of the arc shaped restriction hole by inserting the piston into the restriction hole.
However, rotating speed of the driven side rotating member relative to the drive side rotating member, speed of inserting the piston into the fitting hole and speed of pulling the piston out of the restriction hole are variable according to changes of pressure, temperature and the like of operating oil supplied from a hydraulic pressure supply source. Accordingly, in a structure in which the angular phase of the driven side rotating member relative to the drive side rotating member is locked to the middle angular position when the piston is inserted into the fitting, hole or in a structure in which the angular phase of the driven side rotating member relative to the drive side rotating member is restricted within the angular range defined by opposite ends of the arc shaped restriction hole when the piston is inserted into the restriction hole, it sometimes happens that the piston passes the fitting or restriction hole before the piston is inserted into the hole or the piston is unlikely pulled out of the hole since the drive side rotating member excessively rotates relatively to the drive side rotating member before the piston has been pulled out of the hole.
An object of the present invention is to provide a valve timing adjusting apparatus in which a lock piston can be fitted in or pulled out of a fitting hole without fail.
Another object of the present invention is to provide a valve timing adjusting apparatus in which a restriction piston can be inserted into or pulled out of a restriction hole without fail.
A further object of the present invention is to provide a method of controlling the valve timing adjusting apparatus.
To achieve the above object, a valve timing adjusting apparatus disposed between a drive shaft of an internal combustion engine and a driven shaft causing an opening and closing operation of at least one of an intake valve and an exhaust valve and operative to change an angular phase of the driven shaft relative to the drive shaft so that opening and closing timing of the at least one of an intake valve and an exhaust valve may be varied has drive and driven side rotating members, rotation control pressure chamber, a lock piston, a fitting hole and an angular phase locking pressure chamber.
The drive side rotating member is rotated together with the drive shaft. The driven side rotating member is rotated together with the driven shaft. The rotation control pressure chamber is operative to rotate the driven side rotating member relative to the drive side rotating member so that angular phase of the driven side rotating member relative to the drive side rotating member is controlled to a target position between the most retard angle position and the most advanced angle position in response to hydraulic pressure applied thereto. The lock piston is provided in one of the driven and drive side rotating members. The fitting hole is provided in the other of the driven and drive side rotating members. The angular phase locking pressure chamber is operative to execute one of first and second operations when hydraulic pressure is applied thereto and the other of the first and second operations when application of the hydraulic pressure thereto is released. The first operation is to insert the lock piston into the fitting hole so as to lock the angular phase of the driven side rotating member relative to the drive side rotating member to a middle position between the most retard angle position and the most advanced angle position, and the second operation is to pull the lock piston out of the fitting hole so as to release lock of the angular phase of the driven side rotating member relative to the drive side rotating member at the middle position.
With the valve timing adjusting apparatus mentioned above, a supply route of the hydraulic pressure to the rotation control pressure chamber is different from that to the angular phase locking pressure chamber and, when at least one of the first and second operations is executed, start timing of rotation of the driven side rotating member relative to the drive side rotating member so as to change the angular phase of the driven side rotating member relative to the drive side rotating member to the target position is retard by a given delay time from start timing of execution of the at least one of the first and second operations.
It is preferable that the lock piston is provided at an axial end thereof with a tapered portion whose diameter is smaller toward the round hole, the fitting hole is provided at an opening end thereof with a chamfering portion whose diameter is larger toward the piston, and, when the first operation is executed, the given delay time by which the start timing of rotation of the driven side rotating member relative to the drive side rotating member is retard from the start timing of execution of the first operation is larger than time required for the tapered portion to pass the chamfering portion after the first operation starts.
When the intake or exhaust valve is driven, the driven shaft receives fluctuating torque acting in retard or advanced angle direction. Since average of the fluctuating torque acts in a retard angle direction, the driven side rotating member receives the fluctuating torque which causes the angular phase of the driven side rotating member relative to the drive side rotating member to change in retard angle direction.
Accordingly, it is preferable that, after the second operation starts, the hydraulic pressure is applied to the rotation control pressure chamber in such a manner that the angular phase of the driven side rotating member relative to the drive side rotating member is kept at the middle position between the most retard angle position and the most advanced angle position or temporarily moved to a position slightly shifted from the middle position toward the advanced angle position before the given delay time lapses. Since the fluctuating torque acting on the driven side rotating member in retard angle direction is reduced, the lock piston can be pulled out of the fitting hole with less frictional resistance.
A rotation speed of the driven side rotating member relative to the drive side rotating member and a moving speed of the lock piston are variable according to change of pressure of the operation oil. Further, the rotation speed of the driven side rotating member relative to the drive side rotating member and the moving speed of the lock piston are also variable according to change of viscosity of the operation oil that is changed by temperature of the operation oil.
Accordingly, it is preferable that the given delay time by which the start timing of rotation of the driven side rotating member relative to the drive side rotating member is retard from the start timing of execution of the at least one of the first and second operations is determined by sensor signals representing pressure and temperature of fluid applied to at least one of the rotation control pressure chamber and the angular phase locking pressure chamber.
Preferably, the valve timing adjusting apparatus further has a restriction piston, a restriction hole and an angular phase restriction pressure chamber. The restriction piston is provided in one of the driven and drive side rotating members. The restriction hole is formed in shape of an arc extending within a given angular range and provided in the other of the driven and drive side rotating members. The angular phase restriction pressure chamber is operative to execute one of third and fourth operations when hydraulic pressure is applied thereto and the other of the third and fourth operations when application of the hydraulic pressure thereto is released. The third operation is to insert the restriction piston into the restriction hole so as to restrict rotation of the driven side rotating member relative to the drive side rotating member within the given angular range and the fourth operation is to pull the restriction piston out of the restriction hole so as to release restriction of rotation of the driven side rotating member relative to the drive side rotating member within the given angular range. With the construction mentioned above, a supply route of the hydraulic pressure to the angular phase restriction pressure chamber is same as that to the angular phase locking pressure chamber, an end of the given angular range is at a position corresponding to the middle position between the most retard angle position and the most advanced angle position and the other end of the given angular range is at a position away from the middle position toward the most advanced angle position and, when the third operation is executed together with the first operation, the restriction piston abuts on the end of the given angular range within the restriction hole.
As an alternative, a valve timing adjusting apparatus disposed between a drive shaft of an internal combustion engine and a driven shaft causing an opening and closing operation of at least one of an intake valve and an exhaust valve and operative to change an angular phase of the driven shaft relative to the drive shaft so that opening and closing timing of the at least one of an intake valve and an exhaust valve may be varied has drive and driven side rotating members, rotation control pressure chamber, a restriction piston, a restriction hole and an angular phase restriction pressure chamber.
The drive side rotating member is rotated together with the drive shaft. The driven side rotating member is rotated together with the driven shaft. The rotation control pressure chamber is operative to rotate the driven side rotating member relative to the drive side rotating member so that angular phase of the driven side rotating member relative to the drive side rotating member is controlled to a target position between the most retard angle position and the most advanced angle position in response to hydraulic pressure applied thereto. The restriction piston is provided in one of the driven and drive side rotating members. The restriction hole is provided in the other of the driven and drive side rotating members. The angular phase restriction pressure chamber is operative to execute one of first and second operations when hydraulic pressure is applied thereto and the other of the first and second operations when application of the hydraulic pressure thereto is released. The first operation is to insert the restriction piston into the restriction hole so as to restrict rotation of the driven side rotating member relative to the drive side rotating member within the given angular range and the fourth operation being to pull the restriction piston out of the restriction hole so as to release restriction of rotation of the driven side rotating member relative to the drive side rotating member within the given angular range.
With the valve timing adjusting apparatus mentioned above, a supply route of the hydraulic pressure to the rotation control pressure chamber is different from that to the angular phase restriction pressure chamber and, when at least one of the first and second operations is executed, start timing of rotation of the driven side rotating member relative to the drive side rotating member so as to change the angular phase of the driven side rotating member relative to the drive side rotating member to the target position is retard by a given delay time from start timing of execution of the at least one of the first and second operations.
When the first operation is executed, the hydraulic pressure is applied to the rotation control pressure chamber in such a manner that, if the restriction piston is outside the given angular range of the restriction hole, the angular phase of the driven side rotating member relative to the drive side rotating member is temporarily moved to a position slightly inside the given angular range of the restriction hole before the given delay time lapses, whereby, when the driven side rotating member is rotated relatively to the drive side rotating member after the given delay time lapses, the target position of the angular phase of the driven side rotating member relative to the drive side rotating member is restricted within the given angular range since the restriction piston abuts on the retard angle side end or the advanced angle side end.
Further, it is preferable that, after the second operation starts, the hydraulic pressure is applied to the rotation control pressure chamber in such a manner that, before the given delay time lapses, the angular phase of the driven side rotating member relative to the drive side rotating member is temporarily moved to a position slightly away inward from the retard angle side end or the advanced angle side end of the restriction hole on which the restriction piston abuts so as to pull smoothly the restriction piston out of the restriction hole.
Preferably, the given delay time by which the start timing of rotation of the driven side rotating member relative to the drive side rotating member is retard from the start timing of execution of the at least one of the first and second operations is determined by sensor signals representing pressure and temperature of fluid applied to at least one of the rotation control pressure chamber and the angular phase restriction pressure chamber.
The valve timing adjusting apparatus further has a lock piston, a fitting hole and an angular phase locking pressure chamber. The lock piston is provided in one of the driven and drive side rotating members. The fitting hole is provided in the other of the driven and drive side rotating members. The angular phase locking pressure chamber is operative to execute one of third and fourth operations when hydraulic pressure is applied thereto and the other of the third and fourth operations when application of the hydraulic pressure thereto is released. The third operation is to insert the lock piston into the fitting hole so as to lock the angular phase of the driven side rotating member relative to the drive side rotating member to a given position within the given angular range of the restriction hole and the second operation is to pull the lock piston out of the fitting hole so as to release lock of the angular phase of the driven side rotating member relative to the drive side rotating member at the given position.
With the construction mentioned above, a supply route of the hydraulic pressure to the angular phase locking pressure chamber is same as that to the rotation control pressure chamber.